1. Field of the Invention
This invention relates to a vane compressor, and more particularly to a vane compressor having a reduced number of airtight interfaces of component parts which are exposed to space outside the compressor.
2. Description of the Prior Art
FIG. 1 is a longitudinal cross-sectional view showing a conventional vane compressor, and FIG. 2 a view taken on line II--II in FIG. 1.
The vane compressor includes a cam ring 101, a rotor 102 rotatably received in the cam ring, a drive shaft 107 rigidly fitted on the rotor, a front side block 103 secured to a front-side end face of the cam ring 101, a rear side block 104 secured to a rear-side end face of the same, a front head 105 secured to a front-side end face of the front side block 103, and a rear head 106 secured to a rear-side end face of the rear side block 104.
A pair of compression spaces 112 are defined at diametrically opposite locations between an inner peripheral surface of the cam ring 101 and an outer peripheral surface of the rotor 102 (only one of the compression spaces is shown in FIG. 1). The rotor 102 has its outer peripheral surface formed therein with a plurality of vane slits 113, in each of which a vane 114 is radially slidably fitted. Each compression space 112 is divided by the vanes 114 into compression chambers, the volume of each of which is varied with rotation of the rotor 102.
Outlet ports 116 are formed in pair through each of opposite lateral side walls of the cam ring 101 (only one pair of the outlet ports 116 is shown in FIG. 2). The lateral side walls of the cam ring 101 are provided with discharge valve covers 117 each formed integrally with valve stoppers and fixed to the cam ring 101 by bolts 118. Between each lateral wall of the cam ring 101 and an inner wall surface of the discharge valve cover 117, there is formed a discharge space 101c to which refrigerant gas is delivered from the compression chambers via the refrigerant outlet ports 116. The discharge space 101c is provided with discharge valves 119 for opening/closing the refrigerant outlet ports 116, respectively. The discharge valves 119 are fixed to the inner wall surface of the discharge valve cover 117 by respective bolts 120.
A front-side end of the drive shaft 107 is rotatably supported by a radial bearing 108 arranged in the front side block 103. A rear-side end of the drive shaft 107 is rotatably supported by a radial bearing 109 arranged in the rear side block 104. The radial bearings 108, 109 are made of ferrous material. Therefore, the rear and front side blocks 103 and 104 are formed with recesses 103a and 104a to provide spaces for casting bushings 130 and 131 formed of ferrous material therein, respectively, so as to prevent the radial bearings 108, 109 from becoming loose due to differences in thermal expansion between the bearings 108, 109 and the side blocks 103, 104.
The above vane compressor is a so-called shell-less compressor which has no shell for covering the whole compressor. In other words, the cam ring 101, the front side block 103, the front head 105, the rear side block 104, and the rear head 106 are all exposed to space outside the compressor. Therefore, the compressor has a lot of interfaces between component parts, which require sealing, and is prone to leakage of refrigerant gas.
Except for the few components, such as the drive shaft 107 and the radial bearings 108, 109, most of the main component parts of the compressor, such as the cam ring 101, the front side block 103, the front head 105, the rear side block 104 and the rear head 106, are formed of aluminum-based material. The end faces of the rotor 102 are brought into sliding contact with the rear-side end face of the front side block 103 and the front-side end face of the rear side block 104 during rotation of the rotor 102. This can cause seizure between the rotor 102 and the front and rear side blocks 103 and 104. To avoid this seizure, the rear-side end face of the front side block 103 and the front-side end face of the rear side block 104 require surface treatment (thin coating of a self-lubricating material).
Further, as described above, the conventional vane compressor requires the recesses 103a and 104a to be formed in the side blocks 103, 104 at locations around the bearings 108 and 109, respectively, to provide spaces into which the bushings formed of ferrous material 130, 131 are cast. This inevitably complicates the construction of the compressor and makes the machining of the same troublesome.